New File Format

OneNote 2010 introduces a new file format but never fear,
OneNote 2010 can still read and write the old 2007 format just fine
if you want it to.

What's New?

OneNote 2010's new file format enables several new features
including:

Linked Note Taking. This let's you take
notes in OneNote and have OneNote automatically build links back
to whatever you were viewing while you took those notes. For
example: you might be reviewing an Excel spreadsheet and making
notes on the content - OneNote can automatically build a link
back to the spreadsheet you were looking at when you took those
notes.

Multi-level Sub-Pages. In earlier
versions of OneNote you had pages and sub-pages. Now you can
have an additional level of subpages.

Versioning. OneNote 2010 supports page
versioning in the new file format. Just go to the Share
tab of the Ribbon and in the History group you can find the Page
Versions button. Click that and older versions (if any)
will appear on the page list directly below the current version
of the page, with the date and author name of the older version
in the title.

Recycle Bin. Also in the History
group you'll see another feature enabled by the 2010 format - a
recycle bin for pages you might accidentally delete.

Math Equations. A common request in
previous versions of OneNote was better support for math and
equations. In OneNote 2010 you get a lot of those features, but
you have to have your notebooks in 2010 format.

There are a few more goodies - for example, using the web app
version of OneNote (coming soon to a browser near you) will require
the notebooks to be in 2010 format.

How Do I Convert?

Converting to/from the OneNote 2010 format is quite simple.
Right-click the notebook in OneNote and choose Properties. In
the bottom right corner you'll see buttons that let you convert a
notebook to 2010 or 2007 format. No point in converting the
notebook to a
format
it's already in so that button will be greyed out.

Just click the button to convert and, after a confirmation
dialog, away we go.

Couple things to note:

In the example above I've selected my "OneNote Mobile"
notebook. That really isn't a very good example because,
at least until you have Windows Mobile 7 with the new OneNote
Mobile capability, you'll want to leave your OneNote Mobile
notebooks in OneNote 2007 format. Otherwise you'll lose
your ability to sync OneNote with your smartphone.

If you're sharing these notebooks with anybody else, make
sure they're all using OneNote 2010. OneNote 2007 won't
work with 2010 formatted notebooks.

If you accidentally convert to 2010 format and want to convert
back, it's easy. Just come right back into Notebook |
Properties and click the button to Convert to 2007.